Method of producing reduced coenzyme q10 as oily product

ABSTRACT

The present invention provides a method for obtaining reduced coenzyme Q 10  which is useful as an ingredient in foods, functional nutritive foods, specific health foods, nutritional supplements, nutrients, drinks, feeds, cosmetics, medicines, remedies, preventive drugs, etc. suited for a commercial scale production in high quality and efficiently.  
     The high-quality oily reduced coenzyme Q 10  which has low viscosity and thereby easily handled may be produced by separating an aqueous phase from the reaction mixture obtainable by oily reacting oxidized coenzyme Q 10  with a reducing agent in water, or by distilling off an coexisting organic solvent at or above the melting temperature of reduced coenzyme Q 10  in concentrating the organic phase containing reduced coenzyme Q 10 . Moreover, a solution or slurry of reduced coenzyme Q 10  may be obtained by adding a desired solvent to the obtained oily product, or a solid of reduced coenzyme Q 10  may be produced by contacting the oily product with a seed crystal.

TECHNICAL FIELD

[0001] The present invention relates to a method of producing reducedcoenzyme Q₁₀. Reduced coenzyme Q₁₀ shows a higher level of oralabsorbability as compared with oxidized coenzyme Q₁₀ and is a compounduseful as an ingredient in good foods, functional nutritive foods,specific health foods, nutritional supplements, nutrients, drinks,feeds, cosmetics, medicines, remedies, preventive drugs, etc.

BACKGROUND ART

[0002] It is known that reduced coenzyme Q₁₀ can be prepared byproducing coenzyme Q₁₀ in the conventional manner, for example bysynthesis, fermentation, or extraction from natural products, andconcentrating a reduced coenzyme Q₁₀-containing eluate fractionresulting from chromatography (JP-A-10-109933). On that occasion, asdescribed in the above-cited publication, the chromatographicconcentration may be carried out after reduction of oxidized coenzymeQ₁₀ contained in the reduced coenzyme Q₁₀ with a conventional reducingagent such as sodium borohydride or sodium dithionite (sodiumhyposulfite), or reduced coenzyme Q₁₀ may be prepared by reacting thereducing agent mentioned above with an existing highly pure grade ofcoenzyme Q₁₀.

[0003] JP-A-57-70834 discloses an example in which reduced coenzyme Q₁₀was synthesized by dissolving coenzyme Q₁₀ in hexane and adding anaqueous solution of sodium hydrosulfite (sodium hyposulfite) in anamount of twice the weight of coenzyme Q₁₀ to the solution, followed bystirring.

[0004] However, the conventional methods require operations such asextraction of the generated reduced coenzyme Q₁₀ with an organic solventand concentration, thus the process time becomes inevitably long, andalso require an expensive production apparatus and large capacity.

[0005] Moreover, when trying to distilling off a solvent from an organicphase containing reduced coenzyme Q₁₀, reduced coenzyme Q₁₀ precipitatesin the form of semi-solid or solid during the operation, which leads totroublesome conditions such as increase of stirring load and stirringfailure, and as a result, the solvent removal tends to be incomplete.Generally, this phenomenon tends to become marked when the purity ofreduced coenzyme Q₁₀ is high.

[0006] Such characteristic of reduced coenzyme Q₁₀ causes a problem notonly in isolating reduced coenzyme Q₁₀ but also in preparing a solutionor slurry of reduced coenzyme Q₁₀ prepared by substituting the solventof the organic phase mentioned above with another solvent, such as thecase of carrying out crystallization. The solvent substitution requiressuch a complicated operation as repeating a solvent removal process withsupplementing a solvent, thus, problems are caused on the commercialscale such as workability, cost efficiency and quality, as describedbelow.

[0007] In the case of substituting a solvent having a high-boiling pointinto a solvent having a low-boiling point or the case that solvents tobe used each other form an azeotrope, solvent substitution becomes anextremely inefficient process which consumes much solvent and a lot oftime. Additionally, unfavorable components or impurities, which coexistsin the solvent to be supplemented (e.g. high-boiling point components orhardly volatile components) accumulate in the solution in a highconcentration. For example, as in a case of substitution of a heptanesolution having a high boiling point to a tetrahydrofuran solutionhaving a low boiling point, the solvent substitution becomes anextremely inefficient, and there is a possibility that stabilizers suchas 2,6-di-tert-butyl-4-hydroxytoluene (BHT), which coexists intetrahydrofuran, accumulate in the solution in a high concentration morethan necessity.

[0008] Moreover, reduced coenzyme Q₁₀ is readily oxidized into oxidizedcoenzyme Q₁₀ by molecular oxygen. On a commercial production scale,complete oxygen elimination is very difficult to achieve and,furthermore, fairly long periods of time are required for individualoperations, unlike laboratory scale production, so that residual oxygenexerts a great adverse effect. The oxidation in question is directlyconnected with such yield and quality problems as the formation ofhardly eliminable oxidized coenzyme Q₁₀ and immixture into the product.For obtaining highly pure reduced coenzyme Q₁₀, it is preferable toshorten the operation time for such as concentration and solventsubstitution in view of adequate protection of the reduced form from theoxidation mentioned above.

[0009] Therefore, it has been desired a method for directly and easilyobtaining reduced coenzyme Q₁₀ without requiring additional operationssuch as extraction with an organic solvent and concentration, etc.,and/or a method for distilling off an organic solvent from the organicphase containing reduced coenzyme Q₁₀ in a convenient manner and in ashort time, without causing stirring failure.

SUMMARY OF THE INVENTION

[0010] In view of the foregoing, the present invention has an object toprovide a method suited for commercial scale production and can givehigh-quality reduced coenzyme Q₁₀ in a convenient and efficient manner.

[0011] As a result of intensive investigations, the present inventorsunexpectedly found that the high-quality reduced coenzyme Q₁₀ can beproduced by reacting oily oxidized coenzyme Q₁₀ with a reducing agent inwater, and thereby completed the present invention useful for theproduction on the commercial scale. The inventors further found thatreduced coenzyme Q₁₀ may be obtained as a oily product with lowviscosity, which is easy to handle, by heating reduced coenzyme Q₁₀ tothe melting temperature or higher (or the temperature to start meltingor higher, when the melting temperature is broad due to a solvent orimpurities contained in reduced coenzyme Q₁₀), thereby completed thepresent invention useful for the production on the commercial scale.

[0012] Thus, the present invention is method for producing reducedcoenzyme Q₁₀ which comprises reacting oily oxidized coenzyme Q₁₀ with areducing agent in water to synthesize oily reduced coenzyme Q₁₀.

[0013] According to the producing method of the present invention, oilyreduced coenzyme Q₁₀ may be obtained by separating an aqueous phase fromthe obtained reaction mixture, and also its crystal may be obtained bycooling the obtained reaction mixture to crystallize reduced coenzymeQ₁₀ in the reaction system.

[0014] By the present invention, it becomes possible to generate reducedcoenzyme Q₁₀ in a reaction system under a reduced atmosphere protectedfrom oxidization, and further to transfer it to a crystalline state insaid reaction system without requiring additional operations such asextraction of reduced coenzyme Q₁₀ into the organic phase, a complicatedsolvent substitution, etc., while dramatically decreasing the operationtime. And the high-quality reduced coenzyme Q₁₀ crystal may be producedefficiently while minimizing formation of by-product oxidized coenzymeQ₁₀ in a sequence of processes from the reduction reaction of reducedcoenzyme Q₁₀ to collecting of reduced coenzyme Q₁₀.

[0015] Moreover, the present invention is a method for obtaining reducedcoenzyme Q₁₀

[0016] which comprises obtaining oily reduced coenzyme Q₁₀ from anorganic phase containing reduced coenzyme Q₁₀ by distilling off anorganic solvent at or above the melting temperature of reduced coenzymeQ₁₀.

[0017] According to the method of the present invention, oily reducedcoenzyme Q₁₀ may be obtained from the organic phase containing reducedcoenzyme Q₁₀ by distilling off an organic solvent in a convenient mannerand in a short time, without causing stirring failure.

[0018] Additionally, oily reduced coenzyme Q₁₀ obtained by one of theabove-mentioned methods maybe made to a solution or slurry containingreduced coenzyme Q₁₀ in a simple manner by adding a desired solvent.Furthermore, reduced coenzyme Q₁₀ may be rapidly solidified and alsoobtained as a crystal by contacting a seed crystal of reduced coenzymeQ₁₀ to the obtained oily reduced coenzyme Q₁₀ at a temperature below themelting temperature of said oily product.

[0019] As described above, by the method of the present invention, notonly additional operations such as extraction into the organic phase ofreduced coenzyme Q₁₀, etc. are not necessary, but also in the caseswhere the organic phase containing reduced coenzyme Q₁₀ is concentrated,the high-quality reduced coenzyme Q₁₀ may be efficiently obtained whiledramatically decreasing operation time and minimizing formation ofby-product oxidized coenzyme Q₁₀ in a sequence of processes through thecollection of reduced coenzyme Q₁₀ without causing problems such asincrease of a stirring load or stirring failure.

[0020] Moreover, by the present invention, reduced coenzyme Q₁₀ may beeasily obtained as a solution or slurry of the desired solvent, and itbecomes possible to carry out the solvent substitution quite efficientlyeven in the cases of substituting solvents having a large difference inboiling points (namely, substitution from a high-boiling point solventto a low-boiling point solvent), or the case solvents to be used eachother form an azeotrope.

DETAILED DESCRIPTION OF THE INVENTION

[0021] In the following, the present invention is described in detail.

[0022] The present invention is intended for producing or obtaining oilyreduced coenzyme Q₁₀ in order to shorten the process time ofconcentration, solvent substitution, etc. in view of favorablyprotecting reduced coenzyme Q₁₀ from oxidization. The present inventionincludes the following two aspects.

[0023] The first aspect is an invention for producing and obtaining oilyreduced coenzyme Q₁₀ by reacting oily oxidized coenzyme Q₁₀ with areducing agent in water, and the second aspect is an invention forproducing or obtaining oily reduced coenzyme Q₁₀ by distilling off anorganic solvent from the organic phase containing reduced coenzyme Q₁₀at or above the melting temperature of reduced coenzyme Q₁₀.

[0024] First of all, the first aspect of the invention for obtainingoily reduced coenzyme Q₁₀ by reacting oily oxidized coenzyme Q₁₀ with areducing agent in water is described.

[0025] In the present invention, reduced coenzyme Q₁₀ is synthesized byreacting oxidized coenzyme Q₁₀ with a reducing agent in water.

[0026] Oxidized coenzyme Q₁₀ used in the present invention may be aproduct comprising oxidized coenzyme Q₁₀ alone as the existinghigh-purity coenzyme Q₁₀ or maybe a mixture comprising oxidized coenzymeQ₁₀ and reduced coenzyme Q₁₀.

[0027] Oily oxidized coenzyme Q₁₀ used in the present invention isobtained by melting oxidized coenzyme Q₁₀ to be oily form, and maycontain various impurities and solvents in such amount that no adverseeffect are occurred on a reaction. However, it is different from asolution which merely dissolves oxidized coenzyme Q₁₀ in an organicsolvent.

[0028] The reaction solvent used in the present invention substantiallyconsists of water alone. Although it may contain a small amount of anorganic solvent, its content is preferably 10 w/w % or less, morepreferably 5 w/w % or less, and still more preferably 1 w/w % or lessrelative to water.

[0029] The reducing agent to be used in the reduction reaction ofoxidized coenzyme Q₁₀ is not particularly restricted, but is preferablyiron (iron as a metal or salt), zinc (zinc as a metal) and hyposulfurousacid or a salt thereof.

[0030] The reduction using iron or zinc is preferably carried out usingan acid. The acid is not particularly restricted but includes, amongothers, fatty acids such as acetic acid, sulfonic acids such asmethanesulfonic acid, and inorganic acids such as hydrochloric acid andsulfuric acid. Inorganic acids are preferred, and sulfuric acid is morepreferred.

[0031] The amount of iron to be used is not particularly restricted but,for example, an amount of about ⅕ by weight or larger based on thecharged weight of oxidized coenzyme Q₁₀ is appropriate for carrying outthe reaction. The upper limit is not particularly restricted but, fromthe economical viewpoint, it is about twice the weight of the abovecharged weight. Iron may be used not only in the form of metallic ironbut also in the form of a salt, for example iron (II) sulfate, etc.

[0032] The amount of zinc to be used is not particularly restricted but,for example, an amount of about {fraction (1/10)} by weight or largerbased on the charged weight of oxidized coenzyme Q₁₀ is appropriate forcarrying out the reaction. The upper limit is not particularlyrestricted but, from the economic viewpoint, it is about twice theweight of the above charged weight.

[0033] The hyposulfurous acid or a salt thereof is not particularlyrestricted but a salt form of hyposulfurous acid is generally used. Thesalt of hyposulfurous acid is not particularly restricted but includes,as preferred species, alkali metal salts, alkaline earth metal salts,ammonium salt and the like. Alkali metal salts such as the lithium salt,sodium salt, and potassium salt are more preferred, and the sodium saltis still more preferred.

[0034] The amount to be used of the hyposulfurous acid or salt is notparticularly restricted but it is not smaller than about ⅕ by weight,preferably not smaller than about ⅖ by weight, and more preferably notsmaller than about ⅗ by weight, based on the charged weight of oxidizedcoenzyme Q₁₀. Larger amounts may be used without causing any particulartrouble, but since such use is economically disadvantageous, the amountto be employed is preferably not larger than about twice the weight ofthe above-mentioned charged weight, more preferably not larger than thecharged weight. Generally, the reaction can be more favorably carriedout with employing an amount within the range of about ⅖ by weight ofthe above-mentioned charge to a weight roughly equal to that of thecharged weight.

[0035] Among the above reducing agents, zinc and hyposulfurous acid or asalt thereof are preferred, and hyposulfurous acid or a salt thereof(specifically hyposulfurous acid) are particularly preferred in view ofthe reduction ability, yield and quality.

[0036] The reduction using the above hyposulfurous acid or a saltthereof is preferably carried out at pH of 7 or lower, more preferablyat pH of 3 to 7, and still more preferably at pH of 3 to 6. The above pHmay be adjusted by using an acid (e.g. mineral acids such ashydrochloric acid and sulfuric acid) or base (e.g. alkaline metalhydroxides such as sodium hydroxide)

[0037] The charging concentration of oxidized coenzyme Q₁₀ in thepresent invention is not particularly restricted, but the upper limit ispreferably 30 w/w %, and more preferably 20 w/w % relative to water. Thelower limit is preferably 1 w/w %, more preferably 5 w/w %, and stillmore preferably 10 w/w % in view of the productivity, etc.

[0038] When the generated reduced coenzyme Q₁₀ is crystallized from saidreaction system after the above reduction reaction, the concentration ofreduced coenzyme Q₁₀ may be appropriately increased or decreased foradjusting/maintaining the slurry concentration and slurry properties ofthe crystallized reduced coenzyme Q₁₀ within a preferable range. Theweight of reduced coenzyme Q₁₀ after the reaction is preferably 20 w/w %or less and more preferably 15 w/w % or less relative to water in viewof the slurry concentration and slurry properties.

[0039] The temperature for the reduction reaction in the presentinvention depends on the purity of oxidized coenzyme Q₁₀ or the ratio ofoxidized coenzyme Q₁₀ and reduced coenzyme Q₁₀, thus cannot beabsolutely specified. It is generally 45° C. or higher, preferably 48°C. or higher and more preferably 50° C. or higher. The upper limit ispreferably the boiling point of the system, more preferably 100° C.,still more preferably 80° C., and particularly preferably 60° C.

[0040] In the practice of the invention, the reduction reaction ispreferably carried out under forced flowing. The power required forstirring to cause such flowing per unit volume is generally not lessthan about 0.01 kW/m³, preferably not less than about 0.1 kW/m³, andmore preferably not less than about 0.3 kW/m³. The above forced flowingis generally caused by the turning of a stirring blade(s). The use of astirring blade(s) is not always necessary if the above flowing can beotherwise obtained. For example a method based on liquid circulation maybe utilized.

[0041] The above reduction reaction can be generally driven tocompletion within 48 hours, preferably within 24 hours, more preferablywithin 10 hours, and still more preferably within 5 hours.

[0042] In the above reduction reaction, especially in the reductionreaction using hyposulfurous acid or a salt thereof, it is exceedinglypreferable to carry out in a deoxygenated atmosphere. It was found thatsuch atmosphere greatly contributes to an improvement in reductionreaction yield and a reduction in reducing agent amount. Thedeoxygenated atmosphere can be attained by substitution with an inertgas, pressure reduction, boiling, or a combination of these. It ispreferable to carry out at least the substitution with an inert gas,namely to use an inert gas atmosphere. As the inert gas, there may bementioned, for example, nitrogen gas, helium gas, argon gas, hydrogengas, and carbon dioxide gas. Nitrogen gas is preferred, however.

[0043] Oily reduced coenzyme Q₁₀ may be obtained by separating anaqueous phase successively from the thus obtained reaction mixture, andif necessary, further by washing with water or brine, etc., for example.It is also possible to crystallize the generated reduced coenzyme Q₁₀ bycooling the above reaction mixture in said reaction system.

[0044] When reduced coenzyme Q₁₀ is obtained as an oily product, theseparation of oily product and aqueous phase and, if needed, washing ofthe oily product are preferably carried out under warmed condition. Thetemperature depends on the purity, etc. of reduced coenzyme Q₁₀ and isnot particularly restricted, but preferably about 45° C. or higher, morepreferably about 48° C. or higher, and still more preferably about 50°C. or higher. The upper limit is preferably a boiling point of thesystem, more preferably about 100° C., still more preferably about 80°C. and particularly preferably about 60° C.

[0045] Moreover, reduced coenzyme Q₁₀ may also be obtained as a crystalby cooling the reaction mixture under reducing atmosphere. The coolingtemperature is not particularly restricted, but preferably below about50° C., more preferably below 48° C., and still more preferably below45° C. The lower limit is a solidifying temperature of the system andmore preferably 0° C. Generally, the cooling is preferably carried outat a temperature range of 0 to 40° C.

[0046] The cooling method for crystallization is not particularlyrestricted, but the cooling is preferably carried out at about 40°C./hour or less, more preferably at about 30° C./hour or less, and stillmore preferably at about 20° C./hour or less. Usually, filterability,slurry properties, etc. in the crystallization of reduced coenzyme Q₁₀carried out in an organic solvent system is poor, thus the handlingproperties is not good in many cases. However, in a practice of thepresent invention, it is possible to obtain a crystal with largeparticle diameter, and these handling properties may be dramaticallyimproved.

[0047] The crystallization of reduced coenzyme Q₁₀ is preferably carriedout under forced flowing. The flowing is generally brought about by astirring power per unit volume of not weaker than about 0.01 kW/m³,preferably not weaker than about 0.1 kW/m³, and more preferably notweaker than about 0.3 kW/m³. The forced flowing is generally provided bythe turning of a stirring blade(s). However, the use of a stirringblade(s) is not always necessary if the above flowing can be otherwiseobtained. For example, it is possible to utilize a method based onliquid circulation.

[0048] As described above, crystallization from a reaction mixture giveshigh-quality reduced coenzyme Q₁₀ crystal while minimizing formation ofby-product oxidized coenzyme Q₁₀.

[0049] Next, the second aspect of the invention for obtaining oilyreduced coenzyme Q₁₀ from an organic phase containing reduced coenzymeQ₁₀ by distilling off an organic solvent at or above the meltingtemperature of reduced coenzyme Q₁₀ is described.

[0050] As mentioned above, reduced coenzyme Q₁₀ which may be used in thepresent invention may be obtained by the conventional methods such assynthesis, fermentation, or extraction from a natural product, forexample. Preferably it may be obtained by reducing oxidized coenzymesQ₁₀ such as an existing highly pure coenzyme Q₁₀ or a mixture ofoxidized coenzyme Q₁₀ and reduced coenzyme Q₁₀ by using a commonreducing agent. Firstly, a method for reducing oxidized coenzyme Q₁₀described.

[0051] Reduced coenzyme Q₁₀ is oxidized with molecular oxygen, andthereby easily produces by-product oxidized reduced coenzyme Q₁₀.Therefore, it is preferable to use a solvent having high ability ofprotecting reduced coenzyme Q₁₀ from oxidization as a solvent for thereduction process. As such solvents, it is preferable to use at leastone species selected from among hydrocarbons, fatty acid esters, ethersand nitriles, and hydrocarbons are most preferable.

[0052] The hydrocarbons are not particularly restricted, but there maybe mentioned, for example, aliphatic hydrocarbons, aromatichydrocarbons, halogenated hydrocarbons, etc. Preferred are aliphatichydrocarbons and aromatic hydrocarbons, and particularly preferred arealiphatic hydrocarbons.

[0053] The aliphatic hydrocarbons are not particularly restricted, andmay be cyclic or acyclic, or saturated or unsaturated. However,generally they contain 3 to 20 carbon atoms, and preferably 5 to 12carbon atoms.

[0054] As specific examples, there may be mentioned, for example,propane, butane, isobutane, pentane, 2-methylbutane, cyclopentane,2-pentene, hexane, 2-methylpentane, 2,2-dimethylbutane,2,3-dimethylbutane, methylcyclopentane, cyclohexane, 1-hexene,cyclohexene, heptane, 2-methylhexane, 3-methylhexane,2,3-dimethylpentane, 2,4-dimethylpentane, methylcyclohexane, 1-heptene,octane, 2,2,3-trimethylpentane, isooctane, ethylcyclohexane, 1-octene,nonane, 2,2,5-trimethylhexane, 1-nonene, decane, 1-decene, p-menthane,undecane, dodecane, etc.

[0055] Among them, saturated aliphatic hydrocarbons having 5 to 8 carbonatoms are more preferred, and preferably used are pentane,2-methylbutane and cyclopentane, which have 5 carbon atoms (referred toas “pentanes”); hexane, 2-methylpentane, 2,2-dimethylbutane,2,3-dimethylbutane, methylcyclopentane, cyclohexane, which have 6 carbonatoms (referred to as “hexanes”); heptane, 2-methylhexane,3-methylhexane, 2,3-dimethylpentane, 2,4-dimethylpentane,methylcyclohexane, which have 7 carbon atoms (referred to as“heptanes”); octane, 2,2,3-trimethylpentane, isooctane,ethylcyclohexane, which have 8 carbon atoms (referred to as octanes);and a mixture of these. In particular, the above heptanes areparticularly preferred since they have a tendency to show a very highprotection effect against oxidization, and heptane is most preferred.

[0056] The aromatic hydrocarbons are not particularly restricted, butgenerally they contain 6 to 20 carbon atoms, preferably 6 to 12 carbonatoms, and particularly preferably 7 to 10 carbon atoms. As specificexamples, there may be mentioned, for example, benzene, toluene, xylene,o-xylene, m-xylene, p-xylene, ethylbenzene, cumene, mesitylene,tetralin, butylbenzene, p-cymene, cyclohexylbenzene, diethylbenzene,pentylbenzene, dipentylbenzene, dodecylbenzene, styrene, etc. Preferredare toluene, xylene, o-xylene, m-xylene, p-xylene, ethylbenzene, cumene,mesitylene, tetralin, butylbenzene, p-cymene, cyclohexylbenzene,diethylbenzene and pentylbenzene. More preferred are toluene, xylene,o-xylene, m-xylene, p-xylene, cumene and tetralin, and most preferred iscumene.

[0057] The halogenated hydrocarbons are not particularly restricted, andmay be cyclic or acyclic, or saturated or unsaturated. But generally,acyclic halogenated hydrocarbons are preferably used. Usually, preferredare chlorinated hydrocarbons and fluorinated hydrocarbons, andchlorinated hydrocarbons are particularly preferred. Preferably, onescontaining 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, andparticularly preferably 1 to 2 carbon atoms are used.

[0058] As specific examples, for example, there may be mentioneddichloromethane, chloroform, carbon tetrachloride, 1,1-dichloroethane,1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane,1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane, pentachloroethane,hexachloroethane, 1,1-dichloroethylene, 1,2-dichloroethylene,trichloroethylene, tetrachloroethylene, 1,2-dichloropropane,1,2,3-trichloropropane, chlorobenzene, 1,1,1,2-tetrafluoroethane, etc.

[0059] Preferred are dichloromethane, chloroform, carbon tetrachloride,1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane,1,1,2-trichloroethane, 1,1-dichloroethylene, 1,2-dichloroethylene,trichloroethylene, chlorobenzene and 1,1,1,2-tetrafluoroethane. Morepreferred are dichloromethane, chloroform, 1,2-dichloroethylene,trichloroethylene, chlorobenzene and 1,1,1,2-tetrafluoroethane.

[0060] The fatty acid esters are not particularly restricted, but theremaybe mentioned, for example, propionates, acetates, formates, etc.Particularly preferred are acetates and formates, and most preferred areacetates. Generally, ester functional groups thereof are notparticularly restricted, but there maybe mentioned alkyl or aralkylgroup having 1 to 8 carbon atoms, preferably alkyl group having 1 to 6carbon atoms, and more preferably alkyl group having 1 to 4 carbonatoms.

[0061] As the propionates, there may be mentioned, for example, methylpropionate, ethyl propionate, butyl propionate, and isopentylpropionate.

[0062] As the acetates, there may be mentioned, for example, methylacetate, ethyl acetate, propyl acetate, isopropyl acetate, butylacetate, isobutyl acetate, sec-butyl acetate, pentyl acetate, isopentylacetate, sec-hexyl acetate, cyclohexyl acetate, benzyl acetate, etc.Preferred are methyl acetate, ethyl acetate, propyl acetate, isopropylacetate, butyl acetate, isobutyl acetate, sec-butyl acetate, pentylacetate, isopentyl acetate, sec-hexyl acetate and cyclohexyl acetate.More preferred are methyl acetate, ethyl acetate, propyl acetate,isopropyl acetate, butyl acetate and isobutyl acetate. Most preferred isethyl acetate.

[0063] As the formates, there may be mentioned, for example, methylformate, ethyl formate, propyl formate, isopropyl formate, butylformate, isobutyl formate, sec-butyl formate, pentyl formate, etc.Preferred are methyl formate, ethyl formate, propyl formate, butylformate, isobutyl formate and pentyl formate, and most preferred isethyl formate.

[0064] The ethers are not particularly restricted, and may be cyclic oracyclic, or saturated or unsaturated. But generally, saturated ones arepreferably used. Usually, ones containing 3 to 20 carbon atoms, andpreferably 4 to 12 carbon atoms and particularly preferably 4 to 8carbon atoms are used.

[0065] As specific examples, there maybe mentioned, for example, diethylether, methyl tert-butyl ether, dipropyl ether, diisopropyl ether,dibutyl ether, dihexyl ether, ethyl vinyl ether, butyl vinyl ether,anisol, phenetole, butyl phenyl ether, methoxytoluene, dioxane, furan,2-methylfuran, tetrahydrofuran, tetrahydropyran, ethylene glycoldimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutylether, ethylene glycol monomethyl ether, ethylene glycol monoethylether, ethylene glycol monobutyl ether, etc.

[0066] Preferred are diethyl ether, methyl tert-butyl ether, dipropylether, diisopropyl ether, dibutyl ether, dihexyl ether, anisol,phenetole, butyl phenyl ether, methoxytoluene, dioxane, 2-methylfuran,tetrahydrofuran, tetrahydropyran, ethylene glycol dimethyl ether,ethylene glycol diethyl ether, ethylene glycol dibutyl ether, ethyleneglycol monomethyl ether and ethylene glycol monoethyl ether. Morepreferred are diethyl ether, methyl tert-butyl ether, anisol, dioxane,tetrahydrofuran, ethylene glycol monomethyl ether and ethylene glycolmonoethyl ether. More preferred are diethyl ether, methyl tert-butylether, anisol, etc., and most preferred is methyl tert-butyl ether.

[0067] The nitriles are not particularly restricted, and may be cyclicor acyclic, or saturated or unsaturated. But generally, saturated onesare preferably used. Usually, ones containing 2 to 20 carbon atoms,preferably 2 to 12 carbon atoms, and particularly preferably 2 to 8carbon atoms are used. As specific examples, there may be mentioned, forexample, acetonitrile, propiononitrile, malononitrile, butyronitrile,isobutyronitrile, succinonitrile, valeronitrile, glutaronitrile,hexanenitrile, heptylcyanide, octylcyanide, undecanenitrile,dodecanenitrile, tridecanenitrile, pentadecanenitrile, stearonitrile,chloroacetonitrile, bromoacetonitrile, chloropropiononitrile,bromopropiononitrile, methoxyacetonitrile, methyl cyanoacetate, ethylcyanoacetate, tolunitrile, benzonitrile, chlorobenzonitrile,bromobenzonitrile, cyanobenzoic acid, nitrobenzonitrile, anisonitrile,phthalonitrile, bromotolunitrile, methyl cyanobenzoate,methoxybenzonitrile, acetylbenzonitrile, naphthonitrile,biphenylcarbonitrile, phenylpropiononitrile, phenylbutyronitrile,methylphenylacetonitrile, diphenylacetonitrile, naphthylacetonitrile,nitrophenylacetonitrile, chlorobenzylcyanide, cyclopropanecarbonitrile,cyclohexanecarbonitrile, cycloheptanecarbonitrile,phenylcyclohexanecarbonitrile, tolylcyclohexanecarbonitrile, etc.

[0068] Preferred are acetonitrile, propiononitrile, succinonitrile,butyronitrile, isobutyronitrile, valeronitrile, methyl cyanoacetate,ethyl cyanoacetate, benzonitrile, tolunitrile and chloropropiononitrile.More preferred are acetonitrile, propiononitrile, butyronitrile andisobutyronitrile, and most preferred is acetonitrile.

[0069] In selecting the solvent to be used from among the solventsmentioned above, such properties as boiling point and viscosity arepreferably taken into consideration (for example, the solvent shouldhave a boiling point which allows appropriate warming for increasing thesolubility and facilitates a solvent removal from wet masses by dryingand solvent recovery from crystallization filtrates (about 30 to 150° C.at 1 atm), a melting point such that solidification hardly occurs inhandling at room temperature as well as upon cooling to room temperatureor below (not higher than about 20° C., preferably not higher than about10° C., still more preferably not higher than about 0° C.), and a lowviscosity (not higher than about 10 cp at 20° C.)). From the industrialoperation viewpoint, a solvent which is hardly volatile at ordinarytemperature is generally preferred; for example, one having a boilingpoint of not lower than about 80° C. is preferred, and one having aboiling point of not lower than about 90° C. is particularly preferred.

[0070] Among the solvents mentioned above, a solvent having lowmiscibility with water is particularly preferably used as a solvent inthe reduction reaction. The solvent in the reduction reaction promotespurifying and obtaining a reduced coenzyme Q₁₀ efficiently, byextracting the reducing agent to be described below and/or impuritiesfrom the reducing agent and removing the same.

[0071] Reduced coenzyme Q₁₀, when in a dissolved state, tends to becomemore resistant to oxidation as the concentration thereof increases.Reduced coenzyme Q₁₀ is highly soluble in the solvents mentioned aboveand, in this respect, too, the above solvents are suitable for theprotection from oxidation. The concentration of reduced coenzyme Q₁₀which is preferred from the viewpoint of protection thereof fromoxidation may vary depending on the solvent species, among others, hencecannot be absolutely specified. Generally, however, the concentration ofreduced coenzyme Q₁₀ in the above solvents is generally not lower than 1w/w %, preferably not lower than 2 w/w %. The upper limit is notparticularly restricted but, from the practical operability viewpoint,it is 400 w/w % or below, preferably 200 w/w % or below, more preferably100 w/w % or below, and still more preferably 50 w/w % or below.

[0072] Thus, when such a solvent as mentioned above is used, it ispossible to minimize the undesirable oxygen-involving side reactionthrough the whole process of the reduction reaction.

[0073] The reduction of oxidized coenzyme Q₁₀ is carried out using, as asolvent, a metal hydride compound, iron (metallic iron or iron in a saltform), zinc (metallic zinc), hyposulfurous acid or a salt thereof, or anascorbic acid or a related compound thereof in the above-mentionedsolvent.

[0074] The metal hydride compound is not particularly restricted butincludes, among others, sodium borohydride and lithium aluminum hydride.The amount to be used of the metal hydride compound may vary dependingon the species thereof, hence cannot be absolutely specified. Generally,however, the reduction can be favorably carried out by using it in anamount of 1 to 3 times the theoretical hydrogen equivalent.

[0075] The reduction using iron or zinc is preferably carried out usingan acid. The acid is not particularly restricted but includes, amongothers, fatty acids such as acetic acid, sulfonic acids such asmethanesulfonic acid, and inorganic acids such as hydrochloric acid andsulfuric acid. Inorganic acids are preferred, and sulfuric acid is morepreferred.

[0076] The amount of iron to be used is not particularly restricted but,for example, an amount of about ⅕ by weight or larger based on thecharged weight of oxidized coenzyme Q₁₀ is appropriate for carrying outthe reaction. The upper limit is not particularly restricted but, fromthe economical viewpoint, it is about twice the weight of the abovecharged weight or lower. Iron may be used not only in the form ofmetallic iron but also in the form of a salt, for example iron (II)sulfate, etc.

[0077] The amount of zinc to be used is not particularly restricted but,for example, an amount of about {fraction (1/10)} by weight or largerbased on the charged weight of oxidized coenzyme Q₁₀ is appropriate forcarrying out the reaction. The upper limit is not particularlyrestricted but, from the economic viewpoint, it is about twice theweight of the above charged weight or lower.

[0078] The hyposulfurous acid or a salt thereof is not particularlyrestricted but a salt form of hyposulfurous acid is generally used. Thesalt of hyposulfurous acid is not particularly restricted but includes,as preferred species, alkali metal salts, alkaline earth metal salts,ammonium salt and the like. Alkali metal salts such as the lithium salt,sodium salt, and potassium salt are more preferred, and the sodium saltis still more preferred.

[0079] The amount to be used of the hyposulfurous acid or salt is notparticularly restricted but it is preferably not smaller than about ⅕ byweight, more preferably not smaller than about ⅖ by weight, and stillmore preferably not smaller than about ⅗ by weight, based on the chargedweight of oxidized coenzyme Q₁₀. Larger amounts may be used withoutcausing any particular trouble, but since such use is economicallydisadvantageous. Thus, the amount to be employed is preferably notlarger than about twice the weight of the above-mentioned chargedweight, more preferably not larger than the charged weight. Generally,there action can be favorably carried out with employing an amountwithin the range of about ⅖ by weight of the above-mentioned charge to aweight roughly equal to that of the charged weight.

[0080] The ascorbic acid or related compounds thereof are notparticularly restricted, and include, for example, not only ascorbicacid, but also rhamno-ascorbic acid, arabo-ascorbic acid, gluco-ascorbicacid, fuco-ascorbic acid, glucohepto-ascorbic acid, xylo-ascorbic acid,galacto-ascorbic acid, gulo-ascorbic acid, allo-ascorbic acid,erythro-ascorbic acid, 6-desoxyascorbic acid, and the like ascorbic acidrelated compounds, and may be ester forms or salts of these.Furthermore, these may be L-form, D-form or racemic form. Specifically,there may be mentioned, for example, L-ascorbic acid, L-ascorbylpalmitate, L-ascorbylstearate, D-arabo-ascorbicacid, etc. In producingthe reduced coenzyme Q₁₀, any of the above-mentioned ascorbic acid andrelated compounds there of may be suitably used. However, thewater-soluble ones are suitably used in particular among theabove-mentioned ascorbic acid or related compounds thereof in view ofseparatability with the generated reduced coenzyme Q₁₀, etc. And mostpreferred is a free form of L-ascorbic acid, D-arabo-ascorbic acid, andthe like in view of the ready availability, price, etc.

[0081] The amount to be used of the ascorbic acid or a related compoundthereof mentioned above is not particularly restricted but may be anamount effective in converting oxidized coenzyme Q₁₀ to reduced coenzymeQ₁₀. It is preferably not smaller than 1 mole, more preferably notsmaller than 1.2 moles, per mole of oxidized coenzyme Q₁₀. The upperlimit is not particularly restricted but, from the economical viewpoint,it is preferably 10 moles, more preferably 5 moles, and still morepreferably 3 moles, per mole of the oxidized coenzyme Q₁₀.

[0082] Among the reducing agent species mentioned above, zinc,hyposulfurous acid and salts thereof, and ascorbic acid and relatedcompounds thereof are preferred from the viewpoint of reducing ability,yield and/or quality, among others, and, in particular, hyposulfurousacid or salts thereof (specifically hyposulfurous acid salts) andascorbic acid or related compounds thereof are preferred.

[0083] In carrying out the reduction reaction, an alcohol and/or waterare/is suitably used singly or in combination, as mentioned below. Wateris preferred in particular when iron, zinc, or hyposulfurous acid or asalt thereof is used as the reducing agent. When a metal hydridecompound or an ascorbic acid or a related compound thereof is used asthe reducing agent, an alcohol can be used in combination. The combineduse of water and an alcohol exhibits the characteristics of both waterand the alcohol and contributes to improvements in reaction rate andyield, among others.

[0084] In the following, a preferred method of reduction is described indetail.

[0085] The reduction using hyposulfurous acid or a salt thereof ispreferably carried out in a mixed solvent system composed of water andat least one organic solvent selected from among the above-mentionedhydrocarbons, fatty acid esters, ethers, and nitrites (preferablyhydrocarbons, more preferably aliphatic hydrocarbons, and among them,still more preferably heptanes and particularly preferably heptane). Onthat occasion, the reaction is preferably carried out preferably at pHof not higher than 7, more preferably at pH 3 to 7, still morepreferably at pH 3 to 6, from the viewpoint of yield, etc. The pH can beadjusted using an acid (e.g. an inorganic acid such as hydrochloric acidor sulfuric acid) or a base (e.g. an alkali metal hydroxide such assodium hydroxide).

[0086] In the reduction using hyposulfurous acid or a salt thereof, theamount of water is not particularly restricted but may be an amount ofwater such that an appropriate amount of the reducing agent, namelyhyposulfurous acid or a salt thereof, can be dissolved therein. Thus, itis preferable that the amount of the hyposulfurous acid or a salt beadjusted preferably to not more than 30 w/w %, and more preferably notmore than 20 w/w %, relative to the weight of water. From theproductivity viewpoint, among others, it is advisable that the amount beadjusted preferably to not less than 1 w/w %, more preferably not lessthan 5 w/w %, and still more preferably not less than 10 w/w %.

[0087] The reduction using the ascorbic acid or a related compoundthereof mentioned above may be preferably carried out using a solventespecially highly miscible with water as selected from among theabove-mentioned hydrocarbons, fatty acid esters, ethers, and nitrites,in particular ethers and nitrites, which are highly miscible with water,and more specifically tetrahydrofuran, dioxane, acetonitrile or thelike. Furthermore, it is particularly preferable to use the alcoholsand/or ketones mentioned below (preferably alcohols and/or ketoneshaving high miscibility with water (specifically, as an alcohol, amonohydric or a dihydric (preferably monohydric) alcohol containing 1 to5 carbon atoms, preferably containing 1 to 4 carbon atoms, and morepreferably containing 1 to 3 carbon atoms, and as a ketone, acetone,methyl ethyl ketone, etc.)). Namely, in the reduction using the ascorbicacid or a related compound thereof, it is preferable to use alcoholsand/or water-soluble organic solvents. Furthermore, from the viewpointof reaction promotion (e.g. reaction temperature lowering or reactiontime shortening) in the production of reduced coenzyme Q₁₀, it is alsopossible to carry out the reduction in the presence of an additivehaving a reaction promoting effect, such as a basic substance or ahydrogen sulfite.

[0088] The basic compound is not particularly restricted but may beeither an inorganic compound or an organic compound. The inorganiccompound is not particularly restricted but includes, among others,hydroxides, carbonates, and hydrogencarbonates of metals (preferablyalkali metals, alkaline earth metals, and the like), and ammonia. Astypical examples thereof, there may be mentioned alkali metal hydroxidessuch as sodium hydroxide, alkali metal carbonates such as sodiumcarbonate, alkali metal hydrogencarbonates such as sodiumhydrogencarbonate, and alkaline earth metal carbonates such as magnesiumcarbonate. The organic compound is not particularly restricted butincludes, among others, amines such as triethylamine. Among the basicsubstances specifically mentioned above, weakly basic substances (weakbases or weak alkalis) such as the carbonates and hydrogencarbonates ofmetals (preferably alkali metals, alkaline earth metals, etc.), ammonia,and like inorganic compounds; amines such as triethylamine, and likeorganic compounds are preferably used. More preferred are the weaklybasic inorganic compounds mentioned above.

[0089] Preferred as the hydrogensulfite are, for example, alkali metalhydrogensulfites such as sodium hydrogensulfite, etc.

[0090] The amount of the additive mentioned above is not particularlyrestricted but may be such that the reaction promoting effect of theadditive can be produced to a desired extent (effective amount). Butgenerally, from the economical viewpoint, the amount is preferably notmore than 20 moles, more preferably not more than 10 moles, still morepreferably not more than 5 moles, and particularly preferably not morethan 2 moles, per mole of the ascorbic acid or a related compoundthereof. The lower limit is not particularly restricted but, preferably,it is 0.01 moles, more preferably 0.05 moles, still more preferably 0.1moles, and particularly preferably 0.2 moles, per mole of the ascorbicacid or a related compound thereof.

[0091] The reduction reaction is preferably carried out under forcedflowing. The power required for stirring to cause such flowing per unitvolume is preferably not less than about 0.01 kW/m³, more preferably notless than about 0.1 kW/m³, and still more preferably not less than about0.3 kW/m³. The above forced flowing is generally caused by the turningof a stirring blade (s). The use of a stirring blade(s) is not alwaysnecessary if the above flowing can be otherwise obtained. For example amethod based on liquid circulation may be utilized.

[0092] The reduction temperature may vary depending on the reducingagent species and/or amount, hence cannot be absolutely specified. Inthe reduction using hyposulfurous acid or a salt thereof, for instance,the reduction is preferably carried out at 100° C. or below, morepreferably at 80° C. or below, still more preferably at 60° C. or below.The lower limit is preferably the solidification temperature of thesystem. Thus, the reduction can be favorably carried out generally atabout 0 to 100° C., preferably at about 0 to 80° C., more preferably atabout 0 to 60° C. In the reduction using an ascorbic acid or a relatedcompound thereof, the reduction is carried out preferably at 30° C. orhigher, more preferably at 40° C. or higher, still more preferably at50° C. or higher. The upper limit is preferably the boiling point of thesystem. Thus, the reduction can be favorably carried out generally atabout 30 to 150° C., preferably about 40 to 120° C., and more preferablyat about 50 to 100° C.

[0093] Generally, the reaction concentration is not particularlyrestricted but the weight of oxidized coenzyme Q₁₀ relative to thesolvent weight is preferably not less than about 1 w/w %, morepreferably not less than 3 w/w %, still more preferably not less than 10w/w %, and particularly preferably not less than 15 w/w %. The upperlimit is not particularly restricted but is preferably not higher thanabout 60 w/w %, more preferably not higher than 50 w/w %, still morepreferably not higher than 40 w/w %, and particularly preferably nothigher than 30 w/w %. Generally, there action can be favorably carriedout at a reaction concentration of about 1 to 60 w/w %, preferably about3 to 50 w/w %, and more preferably about 10 to 40 w/w %.

[0094] The reduction reaction can be driven to completion generallywithin 48 hours, preferably within 24 hours, more preferably within 10hours, and still more preferably within 5 hours.

[0095] An organic phase containing the product reduced coenzyme Q₁₀ isrecovered from the thus-obtained reduction reaction mixture and, ifnecessary (preferably), the organic phase is further washed repeatedlyusing water, brine or the like to achieve complete contaminantelimination.

[0096] It is exceedingly preferable to carry out the above-mentionedreduction reaction and post-treatments in a deoxygenated atmosphere.Surprisingly, it was found that, particularly in the reduction reactionusing hyposulfurous acid or a salt thereof, such atmosphere greatlycontributes to an improvement in reduction reaction yield and areduction in reducing agent amount. The deoxygenated atmosphere can beattained by substitution with an inert gas, pressure reduction, boiling,or a combination of these. It is preferable to carry out at least thesubstitution with an inert gas, namely to use an inert gas atmosphere.As the inert gas, there may be mentioned, for example, nitrogen gas,helium gas, argon gas, hydrogen gas, and carbon dioxide gas. Nitrogengas is preferred, however.

[0097] Secondly, a method for obtaining oily product, a solution andslurry of reduced coenzyme Q₁₀ from the organic phase containing thethus obtained reduced coenzyme Q₁₀ is described.

[0098] The organic phase containing reduced coenzyme Q₁₀ used forobtaining oily reduced coenzyme Q₁₀ is not particularly restricted, butit is preferably an organic solvent having high ability of protectingreduced coenzyme Q₁₀ from oxidization for obtaining the high-qualityreduced coenzyme Q₁₀ while inhibiting an undesirable side reactioncaused by oxygen. Namely, a solution comprising at least one speciesselected from among hydrocarbons, fatty acid esters, ethers and nitrilesis preferred. Among them, as an organic solvent, hydrocarbons and fattyacid esters are preferred, and hydrocarbons are more preferred, andheptanes are most preferred. The organic phase containing reducedcoenzyme Q₁₀ used in the present invention may be either the abovesolution or a condensate obtained by concentrating said solution by acommon method.

[0099] In the present invention, an organic solvent is distilled off ator above the melting temperature of reduced coenzyme Q₁₀, inconcentrating the organic phase containing reduced coenzyme Q₁₀, toremove the coexisting solvent completely or almost completely. Thus,oily reduced coenzyme Q₁₀ is obtained. When the melting temperature isbroad due to a solvent or impurities contained in reduced coenzyme Q₁₀,the temperature for obtaining oily reduced coenzyme Q₁₀ may be atemperature to start melting, or higher.

[0100] In the present invention, the above temperature for obtainingoily reduced coenzyme Q₁₀ depends on the amount of the coexistingorganic solvent, and thus cannot be absolutely specified. But it ispreferably 40° C. or more, more preferably 45° C. or more, still morepreferably 50° C. or more and particularly preferably 60° C. or more.Although it depends on the species and amount of the solvent, thesolvent may be preferably removed at a temperature range of 40 to 140°C., more preferably 40 to 100° C. and still more preferably 50 to 80° C.The above concentration is carried out under normal pressure or reducedpressure.

[0101] By the above method, reduced coenzyme Q₁₀ may be preferablyobtained as oily product while completely distilling off the organicsolvent without causing stirring failure, even in the cases that thepurity of reduced coenzyme Q₁₀ in the organic phase is preferably about80% by weight or more, more preferably about 90% by weight or more, andstill more preferably about 95% by weight or more. The above purity maybe obtained by HPLC as described below.

[0102] Regarding an aspect for obtaining oily reduced coenzyme Q₁₀ byremoving a solvent, the content of the solvent in above-mentioned oilyreduced coenzyme Q₁₀ is preferably 10% by weight or less, morepreferably 5% by weight or less, and still more preferably 2% by weightor less.

[0103] As described above, oily reduced coenzyme Q₁₀ may be obtainedquite conveniently and efficiently by using the above two species ofaspects.

[0104] Moreover, oily reduced coenzyme Q₁₀ obtained by the above aspectsis favorably protected from oxidization by adding a desired solvent sothat reduced coenzyme Q₁₀ should not become oxidized coenzyme Q₁₀, andthus maybe made to a solution or slurry of the high-quality reducedcoenzyme Q₁₀ quite efficiently.

[0105] Particularly, when the organic solvent containing reducedcoenzyme Q₁₀ is substituted with another solvent, the effect of thepresent invention may be performed to the utmost extent by using eitherone of the aspects described below or a combination of two or moreaspects described below.

[0106] The first aspect is an aspect in which the solvent added forobtaining a solution or slurry of reduced coenzyme Q₁₀ has a lowerboiling point than that of the organic solvent to be distilled off.Usually, the substitution of a solvent having a high-boiling point witha solvent having a low-boiling point is inefficient, but it becomespossible to be carried out the substitution efficiently by the presentinvention. For example, there may be mentioned substitutions of heptanewith acetone, toluene with ethanol, ethyl acetate with diethyl ether andheptane with ethanol, and the like.

[0107] The second aspect is an aspect in which the solvent added forobtaining a solution or slurry of reduced coenzyme Q₁₀ forms anazeotrope with the organic solvent to be distilled off. Usually, thesolvent substitution is inefficient by a formation and/or removal of anazeotrope, but it becomes possible to be carried out efficiently by thepresent invention. For example, there may be mentioned substitutions ofheptane with ethanol, chloroform with acetone and ethyl acetate withethanol.

[0108] The third aspect is an aspect in which the solvent added forobtaining a solution or slurry of reduced coenzyme Q₁₀ contains a hardlyvolatile component. The “hardly volatile component” means a componentwhich is hardly distilled off in a usual condition of solventdistillation and solvent substitution, and for example, there may bementioned 2,6-di-tert-butyl-4-hydroxytoluene (BHT) contained in ether asa stabilizer, and the like. In an inefficient solvent substitutioncomprising repeated supplements and removals of a solvent, a hardlyvolatile component tends to accumulate in high concentration in thesolution. For example, when a solvent substitution of heptane withtetrahydrofuran is inefficient, the above BHT can accumulate in highconcentration more than necessary. However, by the present invention,the solvent substitution may be preferably carried out while inhibitingaccumulation of a hardly volatile component.

[0109] The fourth aspect is an aspect in which the solvent added forobtaining a solution or slurry of reduced coenzyme Q₁₀ has a lessability to protect reduced coenzyme Q₁₀ from oxidization than theorganic solvent to be distilled off. In an inefficient solventsubstitution, undesirable side reaction by oxygen tends to occur whilethe solvent substitution over long period of time is carried out undercoexistence of a solvent, which does not have very high protectioneffect from oxidization. However, by the present invention, the solventsubstitution may be preferably carried out while inhibiting theundesirable side reaction by oxygen by minimizing contact time with thesolvent which does not have very high protection effect fromoxidization. For example, there may be mentioned substitutions ofheptane with methyl isobutyl ketone and xylene with dimethylformamide,and the like.

[0110] The solvent added for obtaining a solution or slurry of reducedcoenzyme Q₁₀ is not particularly restricted, but preferably at least onespecies selected from among hydrocarbons, fatty acid esters, ethers andnitrites mentioned above, and also water, alcohols, fatty acids,ketones, nitrogen-containing compounds (except for nitriles),sulfur-containing compounds, etc. More preferably, it is at least onespecies selected from among alcohols, nitriles, ketones, ethers andwater. And particularly preferred are alcohols and/or ketones since theslurry or crystalline properties becomes better.

[0111] The alcohols are not particularly restricted but may be cyclic oracyclic, or saturated or unsaturated. Saturated ones are preferred,however. Generally, they contain 1 to 20 carbon atoms, preferably 1 to12 carbon atoms, more preferably 1 to 6 carbon atoms, and still morepreferably 1 to 5 carbon atoms. Furthermore, dihydric alcoholscontaining 2 to 5 carbon atoms, and the trihydric alcohol containing 3carbon atoms are preferred, among others.

[0112] The monohydric alcohol is not particularly restricted, and theremay be mentioned, for example, methanol, ethanol, 1-propanol,2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol,1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentylalcohol, tert-pentyl alcohol, 3-methyl-2-butanol, neopentyl alcohol,1-hexanol, 2-methyl-1-pentanol, 4-methyl-2-pentanol, 2-ethyl-1-butanol,1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol,2-ethyl-1-hexanol, 1-nonanol, 1-decanol, 1-undecanol, 1-dodecanol, allylalcohol, propargyl alcohol, benzyl alcohol, cyclohexanol,1-methylcyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol,4-methylcyclohexanol, etc.

[0113] Preferred are methanol, ethanol, 1-propanol, 2-propanol,1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol,2-pentanol, 3-pentanol, 2-methyl-1-butanol, isopentyl alcohol,tert-pentyl alcohol, 3-methyl-2-butanol, neopentyl alcohol, 1-hexanol,2-methyl-1-pentanol, 4-methyl-2-pentanol, 2-ethyl-1-butanol andcyclohexanol. More preferred are methanol, ethanol, 1-propanol,2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol,1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol,isopentylalcohol, tert-pentylalcohol, 3-methyl-2-butanol andneopentylalcohol. Still more preferred are methanol, ethanol,1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol,2-methyl-1-butanol and isopentyl alcohol. Most preferred is ethanol.

[0114] The dihydric alcohol is not particularly restricted, and theremay be mentioned, for example, 1,2-ethanediol, 1,2-propandiol,1,3-propandiol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol,2,3-butanediol, 1,5-pentanediol, etc. Preferred are 1,2-ethanediol,1,2-propandiol and 1,3-propandiol, and most preferred is 1,2-ethanediol.The trihydric alcohol is not particularly restricted, and glycerol, etc.may be preferably used, for example.

[0115] The ketones are not particularly restricted, and ones having 3 to6 carbon atoms are preferably used. As specific examples, there may bementioned, for example, acetone, methyl ethyl ketone, methyl butylketone, methyl isobutyl ketone, etc. Preferred are acetone and methylethyl ketone, and most preferred is acetone.

[0116] In a sequence of investigations according to the presentinvention, there is a possibility in a commercial scale production thatreduced coenzyme Q₁₀ melts during a drying process of crystals or longperiod of time is required for drying. Thus, it was found that it wasnot always easy to obtain reduced coenzyme Q₁₀ crystal. However, it wasalso found that the crystal might be rapidly and adequately solidifiedby contacting the above oily reduced coenzyme Q₁₀ with a seed crystal(reduced coenzyme Q₁₀ own crystal) at a temperature below the meltingtemperature of the oily product. Therefore, as an aspect furtherexerting the effect of the present invention, there may be mentioned asolidification method which comprises contacting a seed crystal ofreduced coenzyme Q₁₀ at a temperature below the melting temperature ofoily reduced coenzyme Q₁₀ to solidify it more rapidly and adequately. Bythis method, the solid of reduced coenzyme Q₁₀ may be preferablyobtained in a high yield while preventing losses occurred in ordinarycrystallizations by using organic solvent as well as preventing lossesof agents and time.

[0117] In this case, a solid maybe obtained by forming the above oilyproduct into a desired form after decreasing the temperature of the oilyproduct to below the melting temperature thereof and contacting with theseed crystal. The contact with the seed crystal may be performed eitherbefore or after said formation from the oily product. The solidifyingtemperature is not particularly restricted provided that it is below themelting temperature of the oily product, but generally below 48° C.,preferably below 45° C., and more preferably below 40° C. It isdesirably 0° C. or more.

[0118] The thus-obtained crystals of reduced coenzyme Q₁₀ as mentionedabove can be preferably recovered as a wet product, for example, by sucha solid-liquid separation technique as centrifugation, pressurefiltration, or vacuum filtration, and followed by cake washing. They canbe recovered also as a dry product by further charging the wet productin a reduced pressure drier (vacuum drier) internally purged with aninert gas and drying the same under reduced pressure. The recovery in adry form is preferred.

[0119] When the present invention is practiced in a deoxygenatedatmosphere, the protective effect against oxidation can be furtherincreased. The deoxygenated atmosphere can be attained by inert gassubstitution, pressure reduction, boiling, or a combination of these. Itis preferable to carry out at least the substitution with an inert gas,namely to use an inert gas atmosphere. As the inert gas, there may bementioned, for example, nitrogen gas, helium gas, argon gas, hydrogengas, and carbon dioxide gas. Nitrogen gas is preferred, however.

BEST MODE FOR CARRYING OUT THE INVENTION

[0120] The following examples illustrate the present invention infurther detail. These examples are, however, by no means limitative ofthe scope of the present invention. In the examples, the purity ofreduced coenzyme Q₁₀ and the reduced coenzyme Q₁₀/oxidized coenzyme Q₁₀weight ratio were determined by the HPLC analysis specified below. Thereduced coenzyme Q₁₀ purity values as determined, however, are by nomeans indicative of the limit purity value attainable in accordance withthe present invention. Likewise, the reduced coenzyme Q₁₀/oxidizedcoenzyme Q₁₀ weight ratio values obtained never indicate the upper limitto that ratio.

[0121] (HPLC Conditions)

[0122] Column: SYMMETRY C18 (product of Waters), 250 mm (in length), 4.6mm (in inside diameter); mobile phase: C₂H₅OH:CH₃OH=4:3 (v/v); detectionwavelength: 210 nm; flow rate: 1 ml/min; retention time of reducedcoenzyme Q₁₀: 9.1 min; retention time of oxidized coenzyme Q₁₀: 13.3min.

EXAMPLE 1

[0123] Oxidized coenzyme Q₁₀ (100 g; purity 99.4%) was melted at 50° C.with stirring. While stirring (power required for stirring: 0.3 kW/m³),an aqueous solution prepared by dissolving 100 g of sodium hyposulfite(purity: at least 75%), as the reducing agent, in 1000 ml of water wasgradually added to this oily product and the reduction reaction wascarried out at 50° C. and at pH 4 to 6. After the lapse of 2 hours, themixture was cooled to 2° C. while stirring (power required for stirring:0.3 kW/m³) to give white slurry. All the above operations were carriedout in a nitrogen atmosphere. The slurry obtained was filtered underreduced pressure, and the wet crystals were washed in sequence with coldwater and cold ethanol (the cold solvents used for washing having atemperature of 2° C.). The wet crystals were further dried under reducedpressure (20-40° C., 1-30 mmHg) to give 98 g of white dry crystals(isolated product yield: 98 mole percent). The reduced coenzymeQ₁₀/oxidized coenzyme Q₁₀ weight ratio of the crystals obtained was99.5/0.5, and the purity of the reduced coenzyme Q₁₀ was 99.2%.

EXAMPLE 2

[0124] Oxidized coenzyme Q₁₀ (100 g; purity 99.4%) was melted at 50° C.with stirring. While stirring (power required for stirring: 0.3 kW/m³),an aqueous solution prepared by dissolving 100 g of sodium hyposulfite(purity: at least 75%), as the reducing agent, in 1000 ml of water wasgradually added to this oily product and the reduction reaction wascarried out at 50° C. and at pH 4 to 6. After the lapse of 2 hours, theaqueous phase containing the oily product was removed from the reactionmixture, and 1400 g of ethanol warmed to 50° C. was added. Then, themixture was cooled to 2° C. while stirring (power required for stirring:0.3 kW/m³) to give white slurry. All the above operations were carriedout in a nitrogen atmosphere. The slurry obtained was filtered underreduced pressure, and the wet crystals were washed in sequence with coldethanol, cold water and cold ethanol (the cold solvents used for washinghaving a temperature of 2° C.) The wet crystals were further dried underreduced pressure (20-40° C., 1-30 mm Hg) to give 95 g of white drycrystals (isolated product yield: 95 mole percent). The reduced coenzymeQ₁₀/oxidized coenzyme Q₁₀ weight ratio of the crystals obtained was99.4/0.6, and the purity of the reduced coenzyme Q₁₀ was 99.2%.

EXAMPLE 3

[0125] Oxidized coenzyme Q₁₀ (100 g, purity 99.4%) was melted at 50° C.with stirring. While stirring (power required for stirring: 0.3 kW/m³),an aqueous solution prepared by dissolving 100 g of sodium hyposulfite(purity: at least 75%), as the reducing agent, in 1000 ml of water wasgradually added to this oily product and the reduction reaction wascarried out at 50° C. and at pH 4 to 6. The aqueous phase was removedfrom the reaction mixture containing the oil product, and the oilyproduct was washed 6 times with 1000 g of deaerated saturated brineheated to 50° C. to give oily reduced coenzyme Q₁₀. All the aboveoperations were carried out in a nitrogen atmosphere. To this oilyproduct, ethanol of 25° C. was added to give white slurry of reducedcoenzyme Q₁₀. The slurry obtained was cooled to 2° C., filtered underreduced pressure, and the wet crystals were washed in sequence with coldethanol, cold water and cold ethanol (the cold solvents used for washinghaving a temperature of 2° C.). The wet crystals were further driedunder reduced pressure (20-40° C., 1-30 mmHg) to give 95 g of white drycrystals (isolated product yield: 95 mole percent). The reduced coenzymeQ₁₀/oxidized coenzyme Q₁₀ weight ratio of the crystals obtained was99.4/0.6, and the purity of the reduced coenzyme Q₁₀ was 99.2%.

EXAMPLE 4

[0126] Oxidized coenzyme Q₁₀ (100 g) was melted at 48° C. with stirring.While stirring (power required for stirring: 0.3 kW/m³), an aqueoussolution prepared by dissolving 100 g of sodium hyposulfite (purity: atleast 75%), as the reducing agent, in 1000 ml of water was graduallyadded to this oily product and the reduction reaction was carried out at50° C. and at pH 4 to 6. The aqueous phase was removed from the reactionmixture containing the oily product, and the oily product was washed 6times with 1000 g of deaerated saturated brine heated to 48° C. to giveoily reduced coenzyme Q₁₀. All the above operations were carried out ina nitrogen atmosphere. To this oil, toluene was added to prepare atoluene solution containing reduced coenzyme Q₁₀. The weight ratio ofreduced coenzyme Q₁₀/oxidized coenzyme Q₁₀ in this toluene solution was99.5/0.5.

EXAMPLE 5

[0127] Oily reduced coenzyme Q₁₀ obtained in Example 2 was dripped on aplate (40° C.) on which the reduced coenzyme Q₁₀ own crystal beingspread, then the oily product was rapidly solidified, and a solid in thehemisphere shape was obtained.

COMPARATIVE EXAMPLE 1

[0128] Oily reduced coenzyme Q₁₀ obtained in Example 2 was dripped on aplate (40° C.) on which no reduced coenzyme Q₁₀ own crystal beingspread, and the temperature was maintained for 1 hour, but nosolidification occurred.

EXAMPLE 6

[0129] Oxidized coenzyme Q₁₀ (100 g) was melted at 50° C. While stirring(power required for stirring: 0.3 kW/m³), an aqueous solution preparedby dissolving 60 g of sodium hyposulfite (purity: at least 75%), as thereducing agent, in 1000 ml of water was gradually added to the obtainedoily product and the reduction reaction was carried out at 50° C. and atpH 4 to 6. After the lapse of 2 hours, the aqueous phase containing oilwas removed from the reaction mixture to give oily reduced coenzyme Q₁₀.The reduced coenzyme Q₁₀/oxidized coenzyme Q₁₀ weight ratio in theobtained oily product was 99.3/0.7. All the above operations werecarried out in a nitrogen atmosphere.

EXAMPLE 7

[0130] Oxidized coenzyme Q₁₀ (100 g; purity 99.4%) was dissolved in 1000g of heptane at 25° C. While stirring (power required for stirring: 0.3kW/m³), an aqueous solution prepared by dissolving 100 g of sodiumhyposulfite (purity: at least 75%), as the reducing agent, in 1000 ml ofwater was gradually added and the reduction reaction was carried out at25° C. and at pH 4 to 6. After the lapse of 2 hours, the aqueous phasewas removed from the reaction mixture, and the heptane phase was washed6 times with 1000 g of deaerated saturated brine. All the aboveoperations were carried out in a nitrogen atmosphere. From this heptanesolution, heptane was distilled off under reduced pressure at 50° C. togive oily reduced coenzyme Q₁₀. This oil was easily stirred and brushedaway. The reduced coenzyme Q₁₀/oxidized coenzyme Q₁₀ weight ratio of thecrystals of this oil was 99.5/0.5. The residual amount of heptane was1.3%, and the purity of reduced coenzyme Q₁₀ was without heptane was99.2%.

COMPARATIVE EXAMPLE 2

[0131] A heptane solution of reduced coenzyme Q₁₀ was obtained in thesame manner as in Example 7. Heptane was distilled off from this heptanesolution at 30° C. under reduced pressure. Reduced coenzyme Q₁₀ wasadhered on a wall of the container, and was difficult to brush away.

EXAMPLE 8

[0132] A heptane solution of reduced coenzyme Q₁₀ was obtained in thesame manner as in Example 7. Heptane was distilled off from this heptanesolution at 48° C. under reduced pressure to obtain oily reducedcoenzyme Q₁₀. 1000 g of tetrahydrofuran was added to give atetrahydrofuran solution of reduced coenzyme Q₁₀. The reduced coenzymeQ₁₀/oxidized coenzyme Q₁₀ weight ratio in the solution was 99.5/0.5.

EXAMPLE 9

[0133] Oxidized coenzyme Q₁₀ (100 g; purity 99.4%) was dissolved in 1000g of hexane at 25° C. While stirring (power required for stirring: 0.3kW/m³), an aqueous solution prepared by dissolving 100 g of sodiumhyposulfite (purity: at least 75%), as the reducing agent, in 1000 ml ofwater was gradually added and the reduction reaction was carried out at25° C. and at pH 4 to 6. After the lapse of 2 hours, the aqueous phasewas removed from the reaction mixture, and the hexane phase was washed 6times with 1000 g of deaerated saturated brine. All the above operationswere carried out in a nitrogen atmosphere. From this hexane solution,hexane was distilled off under reduced pressure at 50° C. to give oilyreduced coenzyme Q₁₀. To this oily product, 1000 g of ethanol of 50° C.was added to give an ethanol solution of reduced coenzyme Q₁₀. Thereduced coenzyme Q₁₀/oxidized coenzyme Q₁₀ weight ratio in the solutionwas 99.4/0.6.

EXAMPLE 10

[0134] Oxidized coenzyme Q₁₀ (100 g; purity 99.4%) was dissolved in 1000g of hexane at 25° C. While stirring (power required for stirring: 0.3kW/m³), an aqueous solution prepared by dissolving 100 g of sodiumhyposulfite (purity: at least 75%), as the reducing agent, in 1000 ml ofwater was gradually added and the reduction reaction was carried out at25° C. and at pH 4 to 6. After the lapse of 2 hours, the aqueous phasewas removed from the reaction mixture, and the hexane phase was washed 6times with 1000 g of deaerated saturated brine. All the above operationswere carried out in a nitrogen atmosphere. From this hexane solution,hexane was distilled off under reduced pressure at 50° C. to give oilyreduced coenzyme Q₁₀. To this oily product, 1000 g of ethanol of 25° C.was slowly added to give white slurry of reduced coenzyme Q₁₀. Theslurry obtained was cooled to 2° C., filtered under reduced pressure,and the wet crystals were washed in sequence with cold ethanol, coldwater and cold ethanol (the cold solvents used for washing having atemperature of 2° C.) The wet crystals were further dried under reducedpressure (20-40° C., 1-30 mmHg) to give 95 g of white dry crystals(isolated product yield: 95 mole percent). The reduced coenzymeQ₁₀/oxidized coenzyme Q₁₀ weight ratio of the obtained crystal was99.3/0.7, and the purity of reduced coenzyme Q₁₀ was 99.0%.

EXAMPLE 11

[0135] Reduction and concentration were carried out in the same manneras in Example 7 except that 15 g of zinc power and 1100 g of 2.9 Nsulfuric acid were used as the reducing agent instead of sodiumhyposulfite. The obtained oily reduced coenzyme Q₁₀ was easily stirredand brushed away. The oily reduced coenzyme Q₁₀/oxidized coenzyme Q₁₀weight ratio was 99.4/0.6. The residual amount of heptane was 1.9% andthe purity of reduced coenzyme Q₁₀ without heptane was 99.1%.

EXAMPLE 12

[0136] Oxidized coenzyme Q₁₀ (100 g; purity 99.4%) and 60 g ofL-ascorbic acid were added to 1000 g of ethanol, and the reductionreaction was carried out with stirring at 50° C. After the lapse of 24hours, the reaction mixture was cooled to 50° C. At the same temperatureand under reduced pressure, ethanol was distilled off to give oilyreduced coenzyme Q₁₀. This oily product was washed 6 times with 1000 gof deaerated saturated brine at 48° C., and 1000 g of acetone addedthereto to give an acetone solution of reduced coenzyme Q₁₀. The reducedcoenzyme Q₁₀/oxidized coenzyme Q₁₀ weight ratio in the solution was99.5/0.5.

EXAMPLE 13

[0137] Oily reduced coenzyme Q₁₀ obtained in Example 7 was dripped on aplate (40° C.) on which the reduced coenzyme Q₁₀ own crystal beingspread, then the oily product was rapidly solidified, and a solid in thehemisphere shape was obtained.

COMPARATIVE EXAMPLE 3

[0138] Oily reduced coenzyme Q₁₀ obtained in Example 7 was dripped on aplate (40° C.) on which no reduced coenzyme Q₁₀ own crystal beingspread, and the temperature was maintained for 1 hour, but nosolidification occurred.

REFERENCE EXAMPLE 1

[0139] One gram of reduced coenzyme Q₁₀ (reduced coenzyme Q₁₀/oxidizedcoenzyme Q₁₀ weight ratio=99.6/0.4) was dissolved in 20 g of each ofvarious solvents shown in Table 1 at 25° C. After 24 hours of stirringat 25° C. in the air, the reduced coenzyme Q₁₀/oxidized coenzyme Q₁₀weight ratio in each solution was determined. The results thus obtainedare shown in Table 1. TABLE 1 Solvent R Heptane 99.1/0.9 Hexane 98.7/1.3Toluene 98.8/1.2 Chloroform 98.9/1.1 Ethyl acetate 98.9/1.1 Methyltert-butyl ether 98.6/1.4 Tetrahydrofuran 98.5/1.5

REFERENCE EXAMPLE 2

[0140] One gram of reduced coenzyme Q₁₀ (reduced coenzyme Q₁₀/oxidizedcoenzyme Q₁₀ weight ratio=99.6/0.4) was dissolved in 100 g of each ofvarious solvents shown in Table 2 at 35° C. After 24 hours of stirringat 35° C. in the air, the reduced coenzyme Q₁₀/oxidized coenzyme Q₁₀weight ratio in each solution was determined. The results thus obtainedare shown in Table 2. TABLE 2 Solvent R Heptane 96.7/3.3 Ethyl acetate96.4/3.6 Acetonitrile 96.0/4.0

INDUSTRIAL APPLICABILITY

[0141] The present invention, which has the constitution describedabove, is a method superior in workability on a commercial scale andeconomic efficiency, and can give high-quality reduced coenzyme Q₁₀ inthe form of oil, a crystal, slurry or a solution in a convenient andefficient manner.

1. A method for producing reduced coenzyme Q₁₀ which comprises reactingoily oxidized coenzyme Q₁₀ with a reducing agent in water to synthesizeoily reduced coenzyme Q₁₀.
 2. The method according to claim 1, whereinthe reduction reaction is carried out at 45° C. or higher.
 3. The methodaccording to claim 1, wherein the reducing agent is iron, zinc ordithionous acid or a salt thereof.
 4. The method according to claim 3,wherein the reducing agent is dithionous acid or a salt thereof.
 5. Themethod according to claim 4, wherein the reduction reaction usingdithionous acid or a salt thereof is carried out at pH of 3 to
 7. 6. Themethod according to claim 1, wherein the reduction reaction is carriedout under a deoxygenated atmosphere.
 7. The method according to claim 1,wherein reduced coenzyme Q₁₀ is crystallized in the reaction system bycooling a reaction mixture after the reduction reaction, to obtain thecrystal thereof.
 8. The method according to claim 7, wherein thecrystallization is carried out under a deoxygenated atmosphere.
 9. Themethod according to claim 1, wherein an aqueous phase is separated fromthe reaction mixture after the reduction reaction, to obtain oilyreduced coenzyme Q₁₀.
 10. The method according to claim 9, wherein theobtained oily reduced coenzyme Q₁₀ is added with a solvent to obtain asolution or slurry of reduced coenzyme Q₁₀.
 11. The method according toclaim 9, wherein solid reduced coenzyme Q₁₀ is obtainable by contactinga seed crystal of reduced coenzyme Q₁₀ with the obtained oily reducedcoenzyme Q₁₀ at a temperature below the melting temperature of said oilyreduced coenzyme Q₁₀, followed by solidifying said oily reduced coenzymeQ₁₀.
 12. The method according to claim 9, wherein oil, solution, slurryor solid of reduced coenzyme Q₁₀ is obtained under a deoxygenatedatmosphere.
 13. A method for obtaining reduced coenzyme Q₁₀. whichcomprises obtaining oily reduced coenzyme Q₁₀ from an organic phasecontaining reduced coenzyme Q₁₀ by distilling off an organic solvent ator above the melting temperature of reduced coenzyme Q₁₀.
 14. The methodaccording to claim 13, wherein the purity of reduced coenzyme Q₁₀existing in the organic phase is 80% by weight or more.
 15. The methodaccording to claim 13, wherein the organic solvent is distilled off at40° C. or higher temperature.
 16. The method according to claim 13,wherein a solution or slurry of reduced coenzyme Q₁₀ is obtainable byadding a solvent to the obtained oily reduced coenzyme Q₁₀.
 17. Themethod according to claim 16, wherein the solvent to be added has alower boiling point than that of the organic solvent to be distilledoff.
 18. The method according to claim 16, wherein the solvent to beadded forms an azeotrope with the organic solvent to be distilled off.19. The method according to claim 16, wherein the solvent to be addedcontains a hardly volatile component.
 20. The method according to claim13, wherein the organic phase containing reduced coenzyme Q₁₀ isobtainable by reducing the organic phase containing oxidized coenzymeQ₁₀ using a reducing agent.
 21. The method according to claim 20,wherein the reducing agent is dithionous acid or a salt thereof or anascorbic acid or a related compound thereof.
 22. The method according toclaim 16, wherein the solvent to be added has a less ability to protectreduced coenzyme Q₁₀ from oxidization than the organic solvent to bedistilled off.
 23. The method according to claim 13, wherein the organicsolvent to be distilled off is at least one species selected from thegroup consisting of hydrocarbons, fatty acid esters, ethers andnitrites.
 24. The method according to claim 16, wherein the solvent tobe added is an alcohol.
 25. The method according to claim 16, whereinthe solvent to be added is a ketone.
 26. The method according to claim13, wherein solid reduced coenzyme Q₁₀ is obtainable by contacting aseed crystal of reduced coenzyme Q₁₀ with the obtained oily reducedcoenzyme Q₁₀ at a temperature below the melting temperature of said oilyreduced coenzyme Q₁₀, followed by solidifying said oily reduced coenzymeQ₁₀.
 27. The method according to claim 13 which is carried out under adeoxygenated atmosphere.